Abstract: A pulse-mode data writing protocol is disclosed which reduces the time required to implement a transition in the direction of magnetization of a recording medium, and which reduces the total power required to encode a given data sequence. After a magnetic transition is encoded on the medium by generating a write current pulse through the write head, the write current through the recording head is reduced, thereby utilizing the spatial extent of the write bubble to encode the lack of a transition on the medium. Alternate configurations are disclosed for various scenarios of write bubble size versus maximum cell size, all utilizing the principle of the invention.

Abstract: A novel magnetic data storage method is disclosed for storing digital data in a magnetic medium. According to the present invention, the digital data is represented by the interval between two consecutive biphasic magnetic pulses recorded in the magnetic medium. In addition, additional data can be encoded in the pulse width of each biphasic magnetic pulse so that higher data encoding ratio can be achieved.

Abstract: A method for write-precompensating a waveform for magnetically recording a waveform on a magnetic medium is disclosed. A user data stream is encoded into an encoded data stream so that the encoded data stream has no dibits and no consecutive dibits. No delay is applied to a first transition of a dibit of the encoded data stream. An isolated transition of the encoded data stream is delayed by a first predetermined amount of time. The second transition of a dibit of the encoded data stream is delayed by a second predetermined amount of time, such that the second predetermined amount of time is substantially twice the first predetermined amount of time. Preferably, the encoded data stream satisfies a predetermined run length limited (RLL) k-constraint of k=13 and a predetermined twins t-constraint of t=15. In one embodiment, the encoded data stream is encoded by a block code at rate 8:10. In another embodiment, the encoded data stream is encoded by a block code at rate 16:19.

Abstract: This invention resolves the limitations of the binary data encoding and storage system by encoding multi-valued meaning to data elements prior to the recording and storing of these multi-valued data elements based on a plurality of quantities in a memory point. In order to make a single memory point suitable to record multi-valued data elements, where each value has a special meaning in a particular recording, quantities of magnetism or light, like its intensity, shape, etc., are digitized or analogized so that each of the quantities can be recorded and extracted. The invention additionally includes systems and methods for using multi-valued data elements, including wireless transmission.

Abstract: In a digital information recording and reproducing apparatus of a rotary magnetic head type for selecting and recording a plurality of digital information signals having different transmission rates and for selectively reproducing the recorded signal, a high-rate digital information signal and a low-rate digital information signal are inputted for selection of either one thereof to be converted by a recording-system encoder into two channels of recording signals. When recording the high-rate signal, the rotary drum is turned at a rotation speed and the magnetic tape is fed at a feed speed (V1) to conduct 4-track azimuth recording of the signals for each rotation of the rotary drum by the first to fourth magnetic heads.

Abstract: There is disclosed a recording method for performing a DSV control while recording a recording signal generated by inserting a synchronous signal for decoding reproduction data into every predetermined number of code words in a code word string satisfying a predetermined run length restriction rule and to be outputted into a recording medium, when a plurality of coding tables are used to convert an input data word of p-bits to a code word of q-bits (q>p), and the code word string obtained by directly coupling the code words is recorded and reproduced in a recording medium such as an optical disk and magnetic disk, or transmitted via a transmitting portion, wherein the p-bits are 8 bits, the q-bits are 15 bits, and the predetermined run length restriction rule stipulates that a minimum run length of the signal obtained by NRZI-converting the code word excluding the synchronous signal is 3T, and a maximum run length is any one of 11T, 12T, 13T, and 14T.

Abstract: A method for designing a computer program for finding a low-complexity coder for constrained block codes for application to timing recovery or error control in data recording systems. The method includes (1) decomposing an input set of candidate codewords into simple subsets of codewords, (2) providing, for each simple subset of codewords, a respective subset of datawords, and (3) filling in certain coordinates in the datawords by values of certain coordinates in the codewords.

Abstract: A methodology for designing an implementing high rate RLL codes is optimized for application to 10-bit ECC symbols, and provides rate 20/21, rate 50/51, rate 90/91 and other modulation code rates for use in magnetic recording channels. A relatively small subcode encoding—one easy to implement—is applied to a portion of the input stream, and the resulting base codeword is partitioned into nibbles that, in turn, are interleaved among the unencoded ECC symbols. Code constraints on the subcode word nibbles depend upon the values of adjacent unencoded symbols. The resulting codes provide excellent density and error propagation performance.

Abstract: A method for minimizing once per revolution (OPR) positional errors in a single disk servo track writer (STW) comprises clamping a disc having an outer edge in the servo track writer; spinning the disc in the servo track writer at a predetermined speed; measuring distance from the disc edge to a predetermined point to determine peak to peak once per revolution positional error; determining an average once per revolution positional error from the peak to peak once per revolution positional error; and setting a reference position for writing servo tracks on the disc equal to a predetermined track reference plus the average once per revolution positional error. The servo track writer apparatus comprises a spindle motor for supporting and rotating a disc and a distance sensor such as an interferometer mounted a preset distance from the edge of the disc for measuring the once per revolution outer diameter positional error.

Abstract: A detector is provided to detect data values within a data signal that is sampled to provide temporally separated data samples. A first detector portion is configured to determine the location of a first sample vector in a first signal space. A second detector portion is configured to determine the location of a second sample vector in a second signal space. The second detector portion determines the location by using a logic statement to combine a plurality of location indicators. Each location indicator provides the location of the second sample vector relative to a respective boundary surface. The form of the logic statement is independent of the values of the location indicators. In addition, each location indicator is independent of all other location indicators.

Abstract: An encoder is provided that converts data words into code words. The code words, when concatenated together, are such that sub-strings of consecutive first symbols in the code words have no more symbols than a maximum number; sub-strings having the maximum number of consecutive first symbols and beginning at selected locations within the code words appear without restriction, and sub-strings having the maximum number of consecutive first symbols and beginning at locations other than the selected locations appear only where the sub-string is concatenated with an acceptable secondary sub-string. A method is also provided for generating a set of such code words for an encoder.

Abstract: The present invention provides for the compression of digital and analog data for storage and transmission. Analog data in the form of an analog signal is converted into a digital signal by an analog-to-digital converter. The digital signal is then converted into an analog signal having an alternating frequency by a first converter processor and an alternating frequency generator according to a predetermined conversion table. To reproduce the original analog signal, the analog signal having an alternating frequency is first converted back into a digital signal by an alternating frequency measurement means connected to a second converter processor, also in accordance with the predetermined conversion table. The digital signal is then converted to the original analog signal by a digital-to-analog converter.

Abstract: The present invention provides sequence detection which takes into account amplitude and/or time distortions caused by neighboring magnetization regions on the magnetic medium, wherein the distortions in one magnetization region are caused by the closeness of neighboring magnetization transitions on one or both sides thereof. The sequence detection according to the present invention provides an extended state diagram to include the effects of leading and/or trailing magnetization transitions. More particularly, it has been found that accounting for the effects of trailing transitions requires an increase in the number of states in the state diagram used to form the Viterbi detector. Leading transitions are neutralized by increasing the number of branches between states in the Viterbi detector. Increasing the number of branches instead of states keeps the complexity low and thus saves hardware and associated costs.

Abstract: In digital signal recording apparatus using I-NRZI modulation for recording, the need for intermittently reading or intermittently writing buffer storage is eliminated by using parallel-bit precoding to generate the channel words that are selected between for recording. The precoders perform preceding on an accelerated basis using ripple-through integration of the alternate successive bits used to form each channel word. Two precoders generate (n+1)-parallel-bit channel words at a channel word rate slower by a factor of (n+1) than the rate of a system clock for the I-NRZI modulation. This leaves additional time during each channel word interval to carry out a decision procedure, which determines which of the channel words generated by the two precoders is to be selected for recording.

Abstract: A system and method for reading data to and writing data from multi-level (M-ary) partial response channels uses a trellis coder to encode an input bit stream sequence into a stream of multi-level data symbols. The data symbols are written to the partial response channel using any of a number of techniques. Preferably, the trellis coder anticipates the modulation transfer function of the partial response channel in encoding the data. Because the partial response channel has its own transfer function, the relationship between the data read from the channel and the actual input data bits is a function not only of the data encoder but also of the partial response channel. Therefore, a decoder specification used to implement the decoder takes into account the effect of the trellis encoder as well as the effect of the partial response channel.

Abstract: A data storage device 15 comprises a recording head 35 and a recording media comprising a layer of magnetic material having an anisotropy that is substantially perpendicular to a plane of the layer. The device encoder 80 is adapted to provide an encoded data signal for recording data in encoded bit cells on the magnetic media 30, the encoded data signal comprising a sequence of signal transitions comprising added equalization signal transitions, the equalization signal transitions being added so that a plurality of the encoded bit cells comprises an average magnetization field strength that is substantially null.

Abstract: In a coding method which does not restrict a run length of “1” while data is recorded/reproduced, there are such a drawback that when an error correction is carried out, a total number of error data to be corrected is increased, and also errors of not-detectable data are increased. While data is coded, a continuous number of “1” contained in a code word is limited, and then an error correction is carried out inside a coding/decoding process operation. Thus, a recording/reproducing apparatus having a small number of decoding errors is available.

Abstract: A method and apparatus are described which demodulate channel bits modulated by an arbitrary one of two modulation schemes, by making use of a consolidated reference table with a small address space. The method of the invention comprises the steps of: generating first output bits for representing patterns that correspond to patterns represented by first channel bits other than those patterns being unable to exist under first RLL constraints, the first output bits having a lesser number of bits than the first channel bits; and generating second output bits for representing patterns that correspond to patterns represented by second channel bits other than those patterns being unable to exist under second RLL constraints, the patterns represented by the second output bits being located at discontinuous areas of the patterns represented by the first output bits, the second output bits having a lesser number of bits than the second channel bits.

Abstract: In a coding method which does not restrict a run length of “1” while data is recorded/reproduced, there are such a drawback that when an error correction is carried out, a total number of error data to be corrected is increased, and also errors of not-detectable data are increased. While data is coded, a continuous number of “1” contained in a code word is limited, and then an error correction is carried out inside a coding/decoding process operation. Thus, a recording/reproducing apparatus having a small number of decoding errors is available.

Abstract: In order to generate a sampling clock having a higher accuracy, a synchronous signal generating circuit is provided with a phase error detector, detecting a phase error of a read out signal digitized on the basis of FDTS algorithm, and a VCO, controlling an oscillation frequency on the basis of a phase error detected by the phase error detector, to generate a synchronous signal by the VCO. On the basis of the synchronous signal generated by the synchronous signal generating circuit, an ADC digitizes the read out signal. The digitized read out signal is then converted to binary data by a detection circuit.

Abstract: A method and system for overriding error correction capabilities of digital optical media is provided. The overriding of the error correction codes (ECC) is accomplished by causing a non-correctable pattern of erroneous symbols to occur in the ECC codeword. Specific redundancy symbols are replaced with invalid symbols. The non-correctable error pattern is recognized by the ECC decoder as being non-correctable and the ECC decoder does not attempt to change the values of any symbols of an ECC codeword that is contaminated by the detectable non-correctable error pattern.

Abstract: A method of writing data to a magnetic data storage medium is provided. A peak amount of write current is provided to the transducer, after which the amount of write current is reduced to a second amount of write current, lower than the peak amount. In one embodiment, the second amount of write current is then maintained at a steady state value. In one embodiment, the magnitude of the steady state value is greater than the magnitude of the critical current. In one embodiment the magnitude and duration of the peak write current for each transducer are stored in memory and retrieved when the corresponding transducer is selected. Also provided is a disc drive adapted to implement the aforementioned methods.

Abstract: A digital signal recording apparatus includes an amble generator for generating an amble signal representing a bit-sequence amble pattern. The bit-sequence amble patter can be detected and reproduced by a partial-response detection system “PR(1, 0, −1)” as a detected amble pattern having a period of state inversions which is shorter than a period of state inversions in a detected amble pattern corresponding to a recorded amble pattern of alternation of “1” and “0”. The amble signal generated by the amble generator and a first digital information signal are combined into a second digital information signal on a time sharing basis. The second digital information signal is recorded on a magnetic recording medium. For example, the bit-sequence amble pattern represented by the amble signal has repetition of six bits of “111000”.

Abstract: A magnetic recording disk drive has head positioning servo sectors with servo sector numbers (SSNs) that are not recorded on the disk. The SSNs are encoded through the use of multiple servo sector types that are arranged in a specific sequence around the data tracks. The different servo sector types are identified by unique types of servo timing marks (STMs), which are used to locate the servo sectors. The SSNs that are used to identify the servo sectors on the track form a set or code of m fixed n-bit patterns. A SSN is determined when the STM types read from n sequential servo sectors match one of the fixed SSN pattems. A set or code of m servo sectors, where each servo sector is identified by a unique SSN pattern having length n, is denoted as an (m,n,d) code, where d is referred to as the minimum Hamming distance of the code. The Hamming distance between two patterns refers to the number of locations that are different between the two pattems.

Abstract: A device is disclosed for encoding a stream of databits of a binary source signal into a stream of databits of a binary channel signal. The device comprises a merging unit (4′) for merging a 1-bit merging word at equidistant positions in the serial datastream of the binary source signal, so as to obtain a composite binary source signal. A shuffling step is carried out on the composite binary source signal in a shuffling unit (8′). Next a conversion is carried out in a converter unit (10′), resulting in the channel signal (FIG. 2). Further, a decoding device is disclosed for decoding the channel signal obtained by means of the encoding device.

Abstract: A methodology for designing and implementing high rate RLL codes is optimized for application to 10-bit ECC symbols, and provides rate 30/31, rate 40/41, rate 50/51 and much higher modulation code rates for use in magnetic recording channels. A relatively small subcode encoding—one easy to implement—is applied to a portion of the input stream, and the resulting base codeword is partitioned into nibbles that, in turn, are interleaved among the unencoded ECC symbols. Code constraints on the subcode word nibbles depend upon the values of adjacent unencoded symbols. The resulting codes provide excellent density and error propagation performance.

Abstract: A method is disclosed for enforcing run-length limit constraints convolutional codes, comprising the steps of providing a desired run length limit constraint, providing a first convolutional code structure 202, processing data with the first convolutional code structure 202 such that convolutional code structure 202 applies a predetermined patterning to the data, evaluating and processing the data in reference to the desired run length limit constraint such that any of the data that is not compliant with the run length limit constraint is altered to become compliant, further processing said the data by a transceiver 206, providing a second convolutional code structure 204, evaluating the further processed data with convolutional code structure 204 in reference to the predetermined patterning such that data likely to have been previously altered is identified, and processing the further processed data with convolutional code structure 204 in reference to said predetermined patterning such that data identified

Abstract: A circuit (10) and method for dibit detection in a mass data storage device includes concurrently operating magnitude (16), polarity (18), and peak value (20) qualification circuits. The magnitude qualification circuit (16) produces a magnitude qualification output signal when a magnitude of the read back signal exceeds a predetermined magnitude threshold. The polarity qualification circuit produces a polarity qualification output signal when a polarity of the read back signal is of a predetermined polarity. The peak value qualification circuit produces a peak value qualification output signal at a time at which a peak value of the read back signal occurs during a predetermined period. When the magnitude qualification output signal, the polarity qualification output signal, and the peak value qualification output signals simultaneously occur, a dibit detection signal (118) is produced.

Abstract: Parallel processing in the form of two PR4 Viterbi Detectors connected in parallel operates to increase the maximum channel speed of a given data channel of a magnetic media. According to a target equation defined as Read(D)=(1−D2)2Written(D), in which D is the delay of a data of the channel, a first Viterbi Detector processes even data samples of the channel that have been equalized according to the target equation and a second Viterbi Detector connected in parallel processes odd data samples of the channel that have likewise been equalized according to the target equation. The use of two parallel-connected Viterbi Detectors in this fashion allows data to be processed at half-rate rather than full-rate, thereby increasing the overall channel speed.

Abstract: A digital signal recording apparatus includes an amble generator for generating an amble signal representing a bit-sequence amble pattern. The bit-sequence amble patter can be detected and reproduced by a partial-response detection system “PR(1, 0, −1)” as a detected amble pattern having a period of state inversions which is shorter than a period of state inversions in a detected amble pattern corresponding to a recorded amble pattern of alternation of “1” and “0”. The amble signal generated by the amble generator and a first digital information signal are combined into a second digital information signal on a time sharing basis. The second digital information signal is recorded on a magnetic recording medium. For example, the bit-sequence amble pattern represented by the amble signal has repetition of six bits of “11000”.

Abstract: In the transmitter which carries out burst transmission using information data as a packet, if the status is divided into four modes, namely, burst stop mode, burst rising mode, burst continuous mode, and burst falling mode, a waveform shaping equipment designed to read out shaped waveform data for each mode from outputs of either of the two memory tables, the first memory table which holds waveform data for specific data patterns used in common in burst rising mode and burst falling mode and the second memory table which holds waveform data for all data patterns used in the burst continuous mode, or a waveform shaping equipment comprising the third memory table which holds waveform data corresponding to all the data patterns used in the burst rising mode and the fourth memory table which holds waveform data corresponding to all data patterns used in the burst falling mode and generating shaped waveform data by synthesizing the two outputs of the third and the fourth memory tables at the time of burst continu

Abstract: A method for synchronously detecting servo information from a data disk includes reading servo information from a disk and passing the servo information signal through a Viterbi detector. The disk is encoded in a known data format from Gray code data to obtain a servo information signal, the encoded Gray code data being constrained to allow no more and no fewer than two “1” states to sequentially occur. The Viterbi detector is modified to eliminate state changes that do not occur within the constrained encoded Gray code data.

Abstract: A methodology for designing and implementing high rate RLL codes is optimized for application to 8-bit ECC symbols, and provides modulation code rates including rate 32/33; rate 48/49; rate 56/57; rate 72/73; rate 80/81 and other code rates for use in magnetic recording channels. A relatively small subcode encoding—one easy to implement—is applied to a portion of the input stream, and the resulting base codeword is partitioned into nibbles that, in turn, are interleaved among the unencoded ECC symbols. Code constraints on the subcode word nibbles depend upon the values of adjacent unencoded symbols. The resulting codes provide excellent density and error propagation performance.

Abstract: An encoder and a method of encoding successive data words into successive code words for transmission through a channel is provided. The encoder divides each successive data word into first and second portions. The first portion of each successive data word is mapped into a corresponding first code pattern and a corresponding state variable according to a selected code. A second portion of each successive data word is mapped into a corresponding second code pattern that is associated with the state variable, according to the selected code. The first and second code patterns are combined to form each of the successive code words. The successive code words are concatenated to form an encoded bit stream having a plurality of bit positions.

Abstract: A clock signal is easily extracted from a signal transmitted corresponding to a partial response transmission method so as to securely identify bits.As a structure of a recording side, an 8-to-9 converting circuit is connected in series with a pre-coding circuit and a recording amplifier. An output signal of the recording amplifier is recorded on a magnetic tape. A signal reproduced from the magnetic tape is supplied to a reproducing amplifier. On a reproducing side, the reproducing amplifier is connected to a partial response equalizing and Viterbi decoding circuit and a clock extracting circuit. The clock extracting circuit is connected to the partial response equalizing and Viterbi decoding circuit.

Abstract: An apparatus and method are disclosed for reducing the effects of thermal asperities and other anomalous conditions on disc drive read operations. An improved data block format is provided having first and second sync fields in which sync patterns are stored, the first and second sync fields being separated by a selected distance within the data block. The sync pattern of the second sync field enables synchronization of a disc drive read channel to the user data in the data block when the read channel fails to be synchronized by the sync pattern of the first sync field. In one embodiment, control information used by the read channel to prepare for receipt of the user data is stored in a field between the first and second sync fields; in an alternative embodiment, a portion of the user data is stored between the first and second sync fields.

Abstract: A data recording device such as a hard disk apparatus has an orthogonal coding circuit and a modulation circuit. The orthogonal coding circuit encodes recording data to be recorded to adjacent two tracks as two orthogonal code streams which are included in an Hadamard matrix. The modulation circuit outputs recording signals, which are obtained by modulating the code streams using the NRZI system, to a magnetic head. Reproduction signals read out from a magnetic disk by the magnetic head are decoded as recording data based upon given decoding rules according to the two code streams.

Abstract: A signal recording apparatus for a video instrument using a magnetic recording medium which is capable of more accurately computing the signal to be recorded on the tape by correcting the output signal when affixing "1" or "0" after computing the output signal to which the pilot tone is affixed. In addition, one line block is used on the assumption that "1" or "0" is always affixed to the code word.

Abstract: A method of controlling track following in a recorder which uses recording in oblique tracks of a magnetic tape without inactive areas between the tracks and wherein data gaps occur in the useful data sequence due to the change of tracks includes the step of filling the time period containing the data gaps with a predetermined sequence of cyclical modifications of code words representing amplitude and degree increments of a symmetrical train of oscillations. A sequence of code words is used to produce incremental portions of the train of symmetrical oscillations whereby a number of incremental portions forms a complete train of symmetrical oscillations. The code words are modified in synchronism with the clock rate at which the useful data of the recorder are clocked.

Abstract: A device comprises a variable-gain input amplifier, a low-pass analog filter, a transversal continuous-time analog filter, and two distinct and parallel sampling channels interposed between the transversal analog filter and an RLL-NRZ decoder. The two sampling channels each comprise an analog-to-digital converter and a Viterbi detector arranged in series and operating according to sampling sequences that alternate with one another.

Abstract: A method and apparatus for writing binary servo data into the servo bursts contained on the storage medium of a storage device. The binary servo information may include track identifying information such as a track number, cylinder number, head number, sector number, index and/or SID. A burst includes T time slots, each slot comprising one cycle of the servo burst frequency, and the servo data to be written comprises X bits of binary data. Each one-bit of the servo data is represented as a slot containing a transition, and each zero-bit is represented as an empty or null slot. In this manner, the present invention provides a highly bit-efficient scheme for representing digital servo data. A high quality PES signal is assured by writing the binary servo information in such a manner as to guarantee a threshold number of transitions per burst as required for accurate peak-hold detection.

Abstract: A system and method employing a rate 16/17 (0,5) code constructed in accordance with a set of pivot bits and a set of corrections for predefined code violations limits the number of consecutive zeros seen by a channel to five. The rate 16/17 (0,5) code is suitable for magnetic or similar recording media and may be employed in partial response maximum likelihood read channels. A feature of the constructed code is a high transition density which allows for more frequent timing and gain control updates, which results in lower required channel input signal to noise ratio for a given channel performance. Each constructed codeword is block encodable and block decodable, and the code construction allows for efficient circuit implementation in both an encoder and a decoder.

Abstract: A buried servo signal on tape is modulated to provide information. According to the modulation, each of a plurality of sets of cycles has at least a selected cycle modulated to represent at least two modulation values. The modulation of the selected cycles of a group of sets of cycles provides a string of modulation values. The modulation values formed identifiers of longitudinal physical location on tape or other tape identifying information (e.g., number of frames per track and cartridge type code).

Abstract: A servo decoder is disclosed for disc storage systems that operates according to a novel coding scheme capable of accurately decoding detected codewords representing servo track address during seek operations, even when the recording head flies between two adjacent tracks, and capable of correcting errors in the detected codedwords caused by noise in the read signal, such as inter-symbol interference. In a first embodiment, the coding scheme comprises an error correcting code (ECC) capable of correcting a predetermined number of bit errors in the detected codewords. To achieve the equivalent effect of a conventional Gray code, the codewords are arranged such that adjacent track addresses differ by a number of bits equal to the minimum distance of the ECC code. In a second embodiment, the servo code corrects certain minimum distance error events associated with a trellis type sequence detector.

Abstract: A PCI to SCSI host adapter circuit is provided for use with different types of host platforms. The host adapter includes logic and controller circuits, and a memory having multiple drivers and a bank switching instruction set stored therein. During initialization, the first driver is loaded into the host's memory if the host's processor is of a compatible type. Otherwise, the bank switching instruction set is loaded into the host's memory and interpreted by the host's processor. During interpretation, the bank switching instruction set causes the host's processor to signal the logic circuit to request that the controller circuit re-map another driver to the location of the first driver in the memory. After this bank switching has occurred, the selected driver is loaded into the host's memory, provided of course that the host's processor is of a compatible type. This process may be repeated until the appropriate code type is found or the host processor is not supported.

Abstract: A sampled amplitude read channel is disclosed for disk storage systems that employs an EPR4 remod/demod sequence detector. To reduce the complexity of timing recovery, gain control and adaptive equalization, the channel samples are initially equalized into a PR4 partial response so that a simple slicer circuit can generate estimated sample values. The PR4 equalized channel samples are then passed through a 1+D filter to generate EPR4 equalized channel samples which are processed by an EPR4 Viterbi sequence detector to generate a preliminary binary sequence. The preliminary binary sequence is remodulated into an estimated or ideal PR4 sample sequence which is subtracted from the PR4 equalized channel samples to generate an error sample sequence. An error pattern detector processes the error sample sequence to detect the dominant error events associated with the EPR4 Viterbi sequence detector.

Abstract: A hard disk drive read circuit for d=1 run length limited (RLL) encoded data which processes multiple consecutive data samples in parallel. The circuit of the present invention receives an analog signal from the read head of the hard disk drive. The circuit comprises a plurality of digital detection channels, coupled to the analog signal, each channel outputting an alternate bit of digital data represented by the analog signal. A timing circuit, coupled to the plurality of digital detection channels, generates a plurality of timing signals controlling the plurality of digital detection channels. The timing circuit derives timing information from one of the digital detection channels. The d=1 RLL code is modified so that there are at most nine consecutive 0's in the digital data output by the digital detection channel from which the timing circuit derives the timing information. An encoder generates the encoded digital data to be recorded on the hard disk drive.

Abstract: A playback data detecting apparatus comprises a transversal filter 11 for performing partial response equalization, a Viterbi decoding circuit 12 for subjecting the output of the transversal filter 11 to Viterbi decoding, a selected code determination circuit 13 for selecting either (the) (delayed) data of the output of the transversal filter 11 or the output of the Viterbi decoding circuit 12 to determine (the an output corresponding equalization function), a reducing code determination circuit 14 for determining (an output code) by subtracting by the output of the Viterbi decoding circuit 12 (from) (the delayed) data of the output of the transversal filter 11, a (clocked) delaying circuit 15 for delaying the output of the selected code determination circuit 13 and the output of the reducing code determination circuit 14, respectively, and a multiplying coefficient calculating circuit 16 which calculates the optimal multiplying coefficients of the transversal filter 11 for minimizing bit errors from the outp

Abstract: A data receiving channel has a signal converter that converts a received signal into a digital signal. The digital signal is then applied to a Viterbi detector that will provide, as an output, a stream of digital signals that have a maximum likelihood of being accurate. Error correction is performed at the bit level through calculation of the error between the received signal and the maximum likelihood estimate signal produced by the Viterbi detector.

Abstract: Disclosed is a magnetic tape media having addressing data information superimposed on prerecorded track following servo information. The servo information is recorded in magnetic flux transition patterns defining at least one longitudinal servo track. A servo burst pattern of at least two repeated pairs of non-parallel magnetic flux transitions is provided, at least one of which transitions is slanted or otherwise continuously longitudinally variable across the width of the servo track. At least two transitions of the repeated pairs are shifted longitudinally with respect to other of the transitions, the shifted transitions comprising the superimposed addressing data information.